Acoustic diaphragm



H. G. PAPE ACOUSTIC DIAPHRAGM V Filed Jan. 14, 1925 Patented Nov. 20,1928.

I An ideally correct is, which would offer no resistance to deflectains magnetic material in sufficientquantity rangement struments employing magnet poles of greatly.

I of an electrical sound vibrate the diaphragm.

' in the magnetic field are not phragm seat.

1,692,800 UNITED STATES PATENT- OFFICE.

HERMAN G. RAPE, 0F NEWARK, NEW JERSEY.

ACOUSTIC DIAPHRAGM.

- mmon filed January 14, 1925. Serial 110.3358;

in those reproducers of this type whichare in ordinary use.

Fig. 4: is a similar view of the magnet struc- This invention relates to magnetic acoustic diaphragms, such as are used in telephone receivers, radio head phones and kindred speech reproducing appliances. ture wherein a central pole is used.

diaphragm would be one Figs. 5, 6 and 7 are similar views of simfiexibility and resiliency, that ilar types of magnets showing the diversified proportions customarily used in magnet poles tion but which would return instantly to its of this type. normally position on the release of the Fig. 8 is a plan view of. one form of my magnet pull thereon,

with maximum and which further coninvention as it appears applied to that arg of magnet poles shown in Fig. 7. and so arranged as Figs. 9, 10, 11, and 13 are plan views of netic lines of force without loss in the most' various forms of my improved magnetic piles direct path through the diaphragm between, which may be applied to adiaphragm. the magnet poles. I Fig. 12 is a vertical section of-a diaphragm In the use of most thin iron diaphragms showing one form of my improved loading. much of the magnetic force in the magnetic Fig. 14 is a partial vertical section of a field, however, is lost or is ineffective In other words, the vention has been applied. maximum energy of the magnet is not utilized I have found that the efficiency. of a diafor the reason that all of the lines of force phragm of any practical shape is greatly bent, diverted or enhanced by the disposition of the central rough the diaphragm. portion thereof of material which is attracted the increased by but which isnot permanently magnetized by a magnet, (and which will hereinafter be to shunt all of thema'gshunted t invention contemplates utilization of the magnetic force acting on the diaphragm and induced by the magnets customarily used in electrical sound reproducthe material so added does not materially ing devices without interfering materially lessen the flexibilityof the diaphragm. For withthe original, flexibility and resiliency of the purpose of illustration only, I have shown the diaphragm and contemplates further the my. invention applied to directly actuated provision of a diaphragm wherein the tendflat disc diaph'ragms though it is to be underency of the diaphfagm to vibrate at its stood that my invention is applicable as well natural period and the consequent tendency to flat, corrugated, circular, squareftrianguto distort the sound to be" reproduced is sub-- stantially v liminated. My invention conphragms. The magnetic material above templates "further the provision of an ecomentioned may take various forms,- nomical, rapid and efiicient method for the pile of finely divided particles, fine wire disproductignlof such 'dia'phragms. posed in a suitable manner near the central -My ifnproved diaphragm is so designed portion of the diaphragm or a combination that it may be readily applied to various inof wire and finely divided particles.

Due to the wide variation in the types and strength, and proportion ;in' magnets H used in electrical when a'preproducing devices, as illustrated in Figs. plied to magnet olesof any shape or type. 1 to 7 inclusive, I have found it advisable to The various 0 jects of my invention will arrange the magnetic material magnetically be clear from the description which follows reinforcing the diaphragm disc in polygonal and from the drawings, in which, I

Fig. 1 is a plan view of oneltype of the of the disc at which point diversified proportions, shapes, arrangements, and is advantageous,

or circular form at or near the central portion the additional mamagnetic poles of the conventional magnetic terial is in the most direct path of the mag spool head showing a portion of the'dianetic lines of force of all t pes of magnet poles, whereby the energy 0 the magnet inviews of the stead of being largely dissipated, is utilized magnets and the poles thereof, forming part by the diaphragm, and the sound reproducing reproducer, illustrating vibrations of the diaphragm are intensifie how widelythe proportions of the poles vary It will be understood that in radio sound Figs. 2 and 3 are similar called magnetic material) provided that lar, conical, tubular and other shapes of diaw such as a the magnetic reinforcing pi e.

signed to secure maximum reproducers wherein weak electrical currents are used, the amount of magnetic material added would be very small, and that where powerful electrical or magnetic impulses are employed the amount of said material would be large in proportion.

To provide a path for the lines of force which is applicable to the various forms of magnet poles A and B in common use, the magnetic material should be deposited on the diaphragm D in the magnetic field induced by the magnets H, and as nearly as possible a ong paths which are common to the lines of force for any type or shape of magnet. It'will be understood, however, that if a diaphragm is to be used in a single definite unvarying position in connection with a magnet of predetermined force and proportions, the disposition and arrangement of the reinforcing material would then depend upon the positions of the magnetic lines of force of greatest strength. The positions of said lines may be determined by dropping finely divided particles of magnetic material upon a diaphragm arranged on the magnet poles in its predetermined operative position. The particles arrange themselves along the lines of force, and if a sufiicient number of said particles are deposited on the diaphragm, there results what I will call a pile of magnetic material arranged to utilize most effectively the magnetic energy of the particular magnet for that particular position of the diaphragm.

I have found, however, that it is impractical to place a diaphragm on its seat S in contact with or near the magnet poles in exact predetermined position and to retain said diaphragm on its seat in unvarying position. For this reason I prefer to arrange the magnetic material in circular or polygonal form as nearly as possible about the line C common to the variousmagnetic fields at the center of the diaphragm so that the magnetic lines of force of greatest strength, at all times and in all positions of the diaphra m, ass through he arrangement of the pile in the form described has the further advantage that the flexibility of the diaphragm is not materially altered since said diaph netically reinforced, as will be pointed out hereinafter. I prefer to use iron or silicon steel for the magnetic material above referred to. a

In view of the variations in size, p'roportions of the magnets H and A and B, I have designed a wherein the arrangement of the inforcement is substantially a compromise dediaphragm in all positions of the diap the pile is approached wh ragm is not mechanically but only magshape and their polesv magnetic repractical efiiciency ragm and for all types of magnets. I have found it desirable;

projections, or arborescent branches, in the pile radiating from thecenter thereof whereby the resistance to the magnetic flux is gradually increased as-the' periphery of the pile is approached. The points, extensions, branches, or twig-like arborescent projections of little height aid further in increasing the magnetic pull on the diaphragm by the provision of a comparatively large area of more or less owerful magnetic reinforcement and the utilization orbending of those stray lines of force which might otherwise fail to be drawn through -the magnetic pile or the diaphragm.

In Fig. 9 I have illustrated the members W of wire or other suitably shaped magnetic material arranged radially on the diaphragm and have further illustrated the magnetic pile G, the base of which is in the general form of a triangle. N car the ends of the wire W, I have shown a comparatively small amount of finely divided particles branching out therefrom. In this arrangement the lines of force in. the magnetic pile are bent to follow up proximately the path indicated by the circle 0 while the flexibility and resilience of the diaphragm is not lessened to any appreciable degree, since the pile is itself flexible and substantially non-resistant to flexure.

In Fig. lO'the pile G reaches its greatest height around a circle spaced outwardly from In Fig..13 I have illustrated a further modi fication of the form shown in Fig. 11,,wherein a wire of magnetic material in the general form of a pointed star is used in combination with a magnetic pile of finely divided particles.

Fig. 14 shows clearly the variations in the height of the magnetic pile G and shows said pile combined with a ring W of magnetic material preferably circular in form, while Fig.

, 12 shows a series of rings W of. gradually decreasing .height combined with a ile G. In carrying out my improved met rod for the formation of the magnetic pile, and the attachment thereof to the diaphragm,

I prefer to coat the diaphragm near the center thereof with suitable adhesive material which is non-brittle and soft when dry, such as gum rubber, preferably dissolved and in liquid form, and then to drop from said diaphragm a predetermined quantity of finely divided particles on to said diaphragm,

whereby the particles adhere to the diaa point above phragm in an area of predetermined shape and form a pile of substantially the form'of a frustum of ahollow cone. e particles settle to the bottom of the gum rubber and on allowing the solvent of the rubber to evapo- 6 rate a pile is formed yarying in height and incorporated with the diaphragm in such a manner that said pile is extremely flexible. I have found gum rubber the best adhesive to use for this purpose by reason of the fact that the flexibility of the diaphragm remains substantially unaliected 'by the addition thereto of the pile in the manner described. However, if desired, said particles may be dropped on to the diaphragm before the adhesive materialis applied thereto, provided that the diaphragm is first placed in position over the magnet poles, after which the cementing operation may be performed. This process may be varied by the combination of the two methods above described, that is, first forming a pile of predetermined shape and then adding terial pulled into position by the magnets with which the diaphragm is to operate.

The wire W or the plate M may be combined with the finely divided particles at the same time or later, if desired. After the pile has been constructed, if a small quantity of adhesive material is then dropped thereon,

said pile will be caused to cohere and to become secured to the diaphragm in such a manner as to allow the diaphragm to be flexed or to be vibrated by the magnets operating thereon without material resistance thereto,

- since the adhesive is itself flexible and the arrangement of the wire 1s such sistance is offered thereby to the vibration of the diaphragm.

- It will be understood that in place of varnish, other cementing agents, such as, gum, rubber, celluloid or other lacquers, may be I used as adhesives or preservatives.

I have found that by the deposition of the proper quantity of magnetic material in a pile of proper form and height depending on the magnet with which the diaphragm is to be used, the tendency of the diaphragm to vibrate at its natural frequency is practically eliminated whereby the sound reproduction is not distorted or interfered with. I have found further that the volume I sound is greatly increased by reason, I believe,

of the greater utilization of the magnetic enand of the consequent ergy of the magnets,

vibration of the diagreater amplitude of phragm.

It will beseen that the shape of the pile may be predetermined so that my improve diaphragm having a magnet pile thereon may be used in connection with many types 0 magnet poles widely varying in proportions and arrangements.

It will further be seen that various changes may be made' in the method of making the thereto more magnetic ma- 4 that no reof said diaphragm,

gnetic reinforcement and in the shape'and proportions the spirit and scope of this invention as set forth in the appended claims.

I claim:

1. In a sound instrument, a diaphragm having plane'surfac'es free of loading material at the central and outer parts thereof, and magnetic comminuted loading material arranged in a comparatively narrow annular ring concentrically on one of said surfaces about the center of said diaphragm and in a pile for shunting the magnetic lines of force through said pile while substantially .maintaining the resilience and flexibility of said pile being superposed said diaphragm,

to the'said surface of said upon and secured diaphragm and serving tive thickness thereof.

2. A diaphragm adapted to be used in sound instruments wherein the magnet poles have varied proportions, shapes and arrangements, comprising a flexible, resilientdisc, plane vunmarred faces on said disc and a pile of comminuted magnetic material arranged in an annular ring about thecenter of said disc, the height of said pile beingla minimum at the outermost periphery thereof, and varying at points at different radial distances from the center of said diaphragm.

3. A diaphragm for sound instruments having magnetic poles varying in size, shape and arrangement, including a narrow annular pile of comminuted magnetic material formin an approximately circular shunt magnetic path between said poles about the center of said diaphragm.

4. In a diaphragm adapted for operation in 'sound receivers having magnetic poles ya! in in size osition and arran ement,

1n sound receivers varying in size, annular pile of finely divided particles of magnetic material arranged about the center the height of said pile being a minimum at the peripheral edges of said pile, and a maximum between said edges.

6. In a diaphragm, adapted for operatlon in sound receivers having magnetic poles varying greatly in size, position, and arrangement, finely divided particles of material arranged in. an annular pile about the d center of said diaphragm, and a magnetic member arranged on said diaphragm about i the center thereof and incorporated with.

said pile for-decreasing the resistance to the magnetic flux while substantially maintainin the original flexibility and resilience of said diaphragm. Y

thereof without departing from to increase the effec- 7 position and arrangement, an

7 A diaphragm for sound instruments having magnetic poles varying in size, shape and arrangement,1ncluding an annular pile varying in height of magneticmateriahforming an approximately circular shunt magneticpath between said poles, and arranged about the center of said diaphragm and substantially radial extensions at the base of said pile.

'8. A diaphragm including a pile'varying in height of finely divided particles of magnetic material arranged substantially in the form of a ring about the center of said diaphragm.

9. A diaphragm having plane unmarred surfaces and including finely divided magnetic material arranged annularly and concentrically about the center of said diaphragm in a pile of varying height resting on and extending above one of said surfaces and flexible cementitious means for causing said material to adhere together and to one of said surfaces for varying the eifective thickness of said diaphragm at said pile.

10. The method of making an acoustic diaphragm, comprising the provision of a disc, applying gum rubber dissolved in a solvent therefor to the center of said disc, dropping finely divided particles of magnetic material from a point above said disc into said gum rubberwhile the 'disc is in the field of a magring pile 0 net which produces a magnetic field similar to that of the magnet to be used with said diaphragm, allowing said particles to settle in the gum rubber until said particles come to rest and allowing the solvent for the gum rubber to eva rate.

11. A iaphragm for sound instruments having magnetic poles varying in size, shape and arrangement, including an annular loadmagnetic material forming an approximately circular shunt magnetic path between said poles, and arranged about the center of said diaphragm so that said center is free of magnetic materiaL.

12. A diaphragm including a magnetic loading arranged substantially in the form of a ring superimposed upon the surface of and about the center of said diaphragm, and of varying height at different distances from the center. v

13. A diaphragm having plane, unmarred surfaces and including a magnetic loading arranged annularly and concentrically about the center of said diaphragm and extending above one of the said surfaces andflexible cementitious means for securing said loading to the dia hragm.

In testimony whereof I have signed my name to this application.

HERMAN G; PAPE. 

